vlib: add elog events for vlib log entries

Pretty interesting to see how long plugins take to load.

Type: improvement

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: If496eb73b2e1fd9dd714142cd5195fa7ccd93ebd
diff --git a/src/vlib/main.h b/src/vlib/main.h
index c420d5f..766c9ec 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -223,6 +223,7 @@
 
   /* Event logger. */
   elog_main_t elog_main;
+  u32 configured_elog_ring_size;
 
   /* Event logger trace flags */
   int elog_trace_api_messages;